As a high efficiency and environmental friendly separation technique, the membrane separation technology becomes a key technique to solve a series of fundamental problems such as energy, resource and environment problems. During the wastewater treatment with membrane, however, fouling deposited on the membrane surface and in the pores may result in an increased trans-membrane pressure, a reduced membrane flux (separation efficiency) and a quick reduction of membrane treatment ability. Thus the life time of the membrane is shortened and the reliability and economy are badly affected during the membrane separation. Obviously, membrane fouling has become a bottleneck to limit wide application of membrane separation technique. Therefore, it has become key points to control membrane fouling and to increase the antifouling ability of the membrane when membrane is used in the wastewater treatment.
Recently, in order to prevent membrane fouling, a membrane reactor has been developed to achieve multi-functionality and high efficiency of membrane by combining membrane technique and other techniques. Chinese patent application (publication No.: CN101224938A) disclosed a method for restricting the membrane fouling through a photocatalytic oxidation by using nano-materials, in which photocatalytic reactor and membrane bioreactor were combined to treat wastewater. Compared with traditional membrane bioreactor, the membrane flux was increased up to 50%. US patent application (publication No.: US2008237145A) disclosed a water treating method by photocatalytic process and an apparatus therewith, wherein titanium dioxide catalytic particles were loaded in a reactor with tubular membranes so that waster water was treated by combining photocatalytic and membrane separation techniques. The combination of photocatalytic technique improved the antifouling property and separation efficiency of the membrane. But this technique has disadvantages that solar energy was used with a low efficiency and the suspended catalyst is difficult to recover.
US patent application (publication No.: U.S. Pat. No. 6,027,649A) disclosed a membrane reactor constructed with coagulant and microfiltration membrane, which previously absorbs the organic matter in the wastewater with coagulant so as to reduce the membrane fouling. However, there are still the problems of second fouling and additive recovering for the addition of coagulant. Chinese patent application (publication No.: CN101234817A) disclosed a membrane carrier foamless oxygen supply membrane bioreactor, in which organic wastewater was treated by aeration and biofilm decomposing organic compound. US patent application (publication No.: US2004079701A) disclosed a membrane bioreactor for wastewater treatment, wherein a filtration module was immersed into mixed liquor with microorganism and porous carrier and the pollution of membrane module was restricted by the reaction between the addition and organic matter. The membrane bioreactor has a compact structure and can be easily controlled automatically, but there are still problems that the microorganism is difficult to control and bio-pollution is serious.
Chinese patent application (publication No.: CN101104537A) disclosed a water treatment device with an electrocatalysis separation membrane, in which oxidant was produced by nano-polymer material in the external electric field, thus the organic matter in the wastewater can be oxidized so as to achieve the purification of water. This device achieves a combination of degradation of organic matter, purification and disinfection. However, anode used in this device is metal material such as stainless steel and copper, which makes anode easily dissolved and results in secondary fouling and poor operation stability. In addition, the composite of polymeric conductive layer and metal substrate is unstable too.